1. Field of the Invention
The present invention generally relates to an electrically opening and closing mechanism. More specifically, the invention relates to an electrically opening and closing mechanism for opening and closing a foldable image display part of a portable telephone, a portable information terminal or the like with respect to its body, or for opening and closing a lid member or the like which is mounted on an opening portion of a body.
2. Description of the Prior Art
There is known a portable telephone or portable information terminal which has a body serving as an operating part on which a plurality of keys are mounted, and an image display part having a liquid crystal display panel mounted on the end portion of the body so as to be capable of being open and closed, the liquid crystal display panel of the image display part being foldable so as to be piled on the body to be stored. When such a portable telephone or portable information terminal is used, a user generally holds the body in his one hand and opens the image display part with his other hand, so that it is not always easy to handle the portable telephone or portable information terminal with his one hand. Therefore, there has been developed a technique for allowing a user to handle a portable telephone with his one hand so that the folded portable telephone can be open by the force of a spring if only an operating button (an unlocking button) is pushed (see, e.g., Japanese Patent Laid-Open No. 2002-314654).
However, since such a portable telephone is designed to open an image display part, which is folded on a body, by spring force, the body and image display part are designed to be open to a predetermined angular position at a stroke, so that the opening angle between the body and image display part can not be optionally adjusted. Therefore, when a user handles a portable telephone with his one hand, it is desired to provide a technique for allowing an image display part to be rotated to an optional opening angle to be held.